Patent GB-663047-A (GB)
Title: Improvements in or relating to limit-stop devices for motor-driven objects such as power-operated guns
IPC: F41A17/08
Filed: 1948-02-26
Abstract: 663,047. Gun turret control. SPERRY CORPORATION. Feb. 26, 1948. [Oct. 24, 1941] No. 5808/48. Class 92 (i). Relates to apparatus for controlling a power-operated angularly moving object, such as a gun, in which means are provided for retarding and stopping the driving motor on the boundary or limit of a predetermined range of movement such as from zero to 90 degrees elevation. According to the invention, the limit-stop means operates in a zone adjacent to the boundary to control the speed of approach to the limiting position in such manner that every point in the zone the speed towards the boundary is prevented from exceeding a speed dependent on the distance of that point from the boundary which speed decreases to zero as the boundary is reached whereas movement of the object away from the boundary is not hindered. The invention is shown applied to a gun turret operated by hydraulic power. In the form shown, Fig. 1, the guns 29 of an upper gun turret are power driven in azimuth and elevation by operating control handles 39, one for each hand, the handle bar moving as a whole about vertical and horizontal axis to control the movements of the turret in azimuth and elevation respectively. The handle bar through spring-centralized linkages rotates an eccentric gear 55 engaging a pinion 57 on the azimuth shaft 59 and an eccentric gear 105 engaging a pinion 107 on the elevation shaft 109. The eccentric gears provide for a small change in turret velocity when the handle bars are near the zero rate position, and a large change when the handle bars are considerably displaced and the turret is moving rapidly. The shafts 59, 109 enter the control box 60, details of which are shown in Fig. 2, in which azimuth shaft 59 actuates through a centralizing detent 65, a shaft 67 controlling the "A" end 72 Fig. 1, of a variable-speed hydraulic transmission unit of the azimuth Vickers' type driven by a motor 71. Elevation shaft 109, Fig. 2, similarly operates control shaft 115 of the "A" end 117, Fig. 1 of an elevation Vickers' unit driven by the same motor 71. The output of the "B" end 73 of the azimuth unit rotates through a clutch 87 and a gear 77 a further shaft 79 driving the azimuth pinion 25 gearing with a fixed circular rack 21 to rotate the entire turret. Hand gear 85 rotates a disengagable worm 83 which also acts as a turret lock when engaged. The clutch 87 disconnects the hydraulic control when the manual control is used. In a similar manner, the output of the "B" end 121 of the elevation unit actuates the elevation shaft 133 of the guns through shaft 125 and sectors 129. Handwheel 126 provides for manual control. The handle bar 39 therefore provides for a rate control of the guns 29 both in azimuth and elevation, which rate increases with the movement of the handle bar from its zero position. A computing gun sight unit 37 is rotated by a shaft 135 through linkage connected with shaft 133. The gunsight unit is maintained parallel to the guns at all times. Elevation data for the computor is obtained from the shaft 125 by bevel gear 139 and flexible shafts 141, 145. Azimuth data is obtained from shaft 79 by pinion 149 and flexible shaft 151. Range data is obtained from knob 153 actuated by the thumb of the operator and drives a flexible shaft 157. The optical line of sight is deviated from the gun angle for the lead correction as described in Specification 606,656. The limit-stop means in elevation in accordance with the invention and also a fire cut-off means operating under endangering conditions are shown in Fig. 2. The rate-shaft 109 operates valve-control shaft 115 and carries a projection 161 which is engaged by a projection 167 driven by the elevation-angle shaft 141 so that at extreme positions of zero or 90 degrees elevation the elevation rate is reduced to zero. Full rate in the reverse direction is however permitted until projection 167 again engages projection 161. The fire cut-off means comprises a camplate 169 rotatable from the azimuth drive by pinion 173 on shaft 171. The cam-follower 177 translated along a diameter of the plate by a bracket 179 carrying a rack 181 and jointed at 183 for rising and falling movements. The rack is actuated to suit gun elevation by pinion 187. The cam-plate 169 is flat except for a raised portion 189 joined to the flat by a bevel and corresponds in shape to endangering sectors of gun fire, the rod 195 being operated to interrupt switch 197 in the firing circuits of the guns. The invention may also be applied to a spherical gun turret suspended below the aircraft Fig. 5, (not shown), the circular training rack surrounding the turret which is trunnioned in brackets depending from the rack. The variable-rate eccentric gears 55, 105 Fig. 1, are replaced by cranks rotating about eccentric axis the pin of the smaller crank engaging a slot in the larger crank. Specification 461,824 is referred to.